Process depending on plasma discharges sustained by inductive coupling

ABSTRACT

A process for fabricating a product 28, 119. The process comprises the steps of subjecting a substrate to a composition of entities, at least one of the entities emanating from a species generated by a gaseous discharge excited by a high frequency field in which the vector sum of currents to phase and inverse-phase capacitive coupled voltages from the inductive coupling structure can be selectively maintained.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of application Ser.No. 08/567,224 filed Dec. 4, 1995.

BACKGROUND OF THE INVENTION

[0002] This invention relates generally to plasma processing. Moreparticularly, the invention is for plasma processing of devices using aninductive discharge. This invention is illustrated in an example withregard to plasma etching or stripping used in the manufacture ofsemiconductor devices. The invention also is illustrated with regard tochemical vapor deposition (CVD) of semiconductor devices. But it will berecognized that the invention has a wider range of applicability. Merelyby way of example, the invention also can be applied in other plasmaetching applications, and deposition of materials such as silicon,silicon dioxide, silicon nitride, polysilicon, among others.

[0003] Plasma processing techniques can occur in a variety ofsemiconductor manufacturing processes. Examples of plasma processingtechniques occur in chemical dry etching (CDE), ion-assisted etching(IAE), and plasma enhanced chemical vapor deposition (PECVD), includingremote plasma deposition (RPCVD) and ion-assisted plasma enhancedchemical vapor deposition (IAPECVD). These plasma processing techniquesoften rely upon radio frequency power (rf) supplied to an inductive coilfor providing power to gas phase species in forming a plasma.

[0004] Plasmas can be used to form neutral species (i.e., uncharged) forpurposes of removing or forming films in the manufacture of integratedcircuit devices. For instance, chemical dry etching generally depends ongas-surface reactions involving these neutral species withoutsubstantial ion bombardment.

[0005] Ion assisted etching processes, however, rely upon ionbombardment to the substrate surface in defining selected films. Ionbombardment can accelerate gas-surface reaction processes and by doingso can produce highly directional (anisotropic) profiles. But these ionassisted etching processes commonly have a lower selectivity relative toconventional CDE processes. Hence, CDE is often chosen when highselectivity is desired, directionality is not essential and ionbombardment to substrates are to be avoided.

[0006] In other manufacturing processes, ion bombardment to substratesurfaces is often undesirable. This ion bombardment, however, is knownto have harmful effects on properties of material layers in devices andexcessive ion bombardment flux and energy can lead to intermixing ofmaterials in adjacent device layers, breaking down oxide and “wear out,”injecting of contaminative material formed in the processing environmentinto substrate material layers, harmful changes in substrate morphology(e.g. amophotization), etc.

[0007] One commonly used chemical dry etching technique is conventionalphotoresist stripping, often termed ashing or stripping. Conventionalresist stripping relies upon a reaction between a neutral gas phasespecies and a surface material layer, typically for removal. Thisreaction generally forms volatile products with the surface materiallayer for its removal. The neutral gas phase species is formed by aplasma discharge. This plasma discharge can be sustained by a coil(e.g., helical coil, etc.) operating at a selected frequency in aconventional photoresist stripper. An example of the conventionalphotoresist stripper is a quarter-wave helical resonator stripper, whichis described by U.S. Pat. No. 4,368,092 in the name of Steinberg et al.

[0008] Referring to the above, an objective in chemical dry etching isto reduce or even eliminate ion bombardment (or ion flux) to surfacesbeing processed to maintain the desired etching selectivity. Inpractice, however, it is often difficult to achieve using conventionaltechniques. These conventional techniques generally attempt to controlion flux by suppressing the amount of charged species in the plasmasource reaching the process chamber. A variety of techniques forsuppressing these charged species have been proposed.

[0009] These techniques often rely upon shields, baffles, largeseparation distances between the plasma source and the chamber, or thelike, placed between the plasma source and the process chamber. Theconventional techniques generally attempt to directly suppress chargedensity downstream of the plasma source by interfering with convectiveand diffusive transport of charged species. They tend to promoterecombination of charged species by either increasing the surface area(e.g., baffles, etc.) relative to volume, or increasing flow time, whichrelates to increasing the distance between the plasma source and theprocess chamber.

[0010] These baffles, however, cause loss of desirable neutral etchantspecies as well. The baffles, shields, and alike, also are oftencumbersome. Baffles, shields, or the large separation distances alsocause undesirable recombinative loss of active species and sometimescause radio frequency power loss and other problems. These baffles andshields also are a potential source of particulate contamination, whichis often damaging to integrated circuits.

[0011] Baffles, shields, spatial separation, and alike, when used alonealso are often insufficient to substantially prevent unwanted parasiticplasma currents. These plasma currents are generated between the waferand the plasma source, or between the plasma source and walls of thechamber. It is commonly known that when initial charged species levelsare present in an electrical field, the charged species are acceleratedand dissociative collisions with neutral particles can multiply theconcentration of charge to higher levels. If sufficient “seed” levels ofcharge and rf potentials are present, the parasitic plasma in thevicinity of the process wafer can reach harmful charge density levels.In some cases, these charge densities may be similar to or even greaterthan plasma density within the source plasma region, thereby causingeven more ion flux to the substrate.

[0012] Charge densities also create a voltage difference between theplasma source and processing chamber or substrate support, which canhave an additional deleterious effect. This voltage difference enhanceselectric fields that can accelerate extraction of charge from the plasmasource. Hence, their presence often induces increased levels of chargeto be irregularly transported from the plasma source to processsubstrates, thereby causing non-uniform ion assisted etching.

[0013] Conventional ion assisted plasma etching, however, often requirescontrol and maintenance of ion flux intensity and uniformity withinselected process limits and within selected process energy ranges.Control and maintenance of ion flux intensity and uniformity are oftendifficult to achieve using conventional techniques. For instance,capacitive coupling between high voltage selections of the coil and theplasma discharge often cause relatively high and uncontrollable plasmapotentials relative to ground. It is generally understood that a voltagedifference between the plasma and ground can cause damaging high energyion bombardment of articles being processed by the plasma, asillustrated by U.S. Pat. No. 5,234,529 in the name of Johnson. It isfurther often understood that the rf component of the plasma potentialvaries in time since it is derived from a coupling to time varying rfexcitation. Hence, the energy of charged particles from plasma inconventional inductive sources is spread over a relatively wide range ofenergies, which undesirably tends to introduce uncontrolled variationsin the processing of articles by the plasma.

[0014] The voltage difference between the region just outside of aplasma source and the processing chamber can be modified by introducinginternal conductive shields or electrode elements into the processingapparatus downstream of the source. When the plasma potential iselevated with respect to these shield electrodes, however, there is atendency to generate an undesirable capacitive discharge between theshield and plasma source. These electrode elements are often a source ofcontamination and the likelihood for contamination is even greater whenthere is capacitive discharge (ion bombardment from capacitive dischargeis a potential source of sputtered material). Contamination is damagingto the manufacture of integrated circuit devices.

[0015] Another limitation is that shields, baffles or electrode elementsgenerally require small holes therein as structural elements. Thesesmall holes are designed to allow gas to flow therethrough. The smallholes, however, tend to introduce unwanted pressure drops and neutralspecies recombination. If the holes are made larger, the plasma from thesource tends to survive transport through the holes and unwanteddownstream charge flux will often result. In addition, undesirabledischarges to these holes in conductive shields can, at times, producean even more undesirable hollow cathode effect.

[0016] In conventional helical resonator designs, conductive externalshields are interposed between the inductive power applicator (e.g.,coil, etc.) and walls of the vacuum vessel containing the plasma. Avariety of limitations with these external capacitive shielded plasmadesigns (e.g., helical resonator, inductive discharge, etc.) have beenobserved. In particular, the capacitively shielded design often producesplasmas that are difficult to tune and even ignite. Alternatively, theuse of unshielded plasma sources (e.g., conventional quarter-waveresonator, conventional half-wave resonator, etc.) attain a substantialplasma potential from capacitive coupling to the coil, and hence areprone to create uncontrolled parasitic plasma currents to groundedsurfaces. Accordingly, the use of either the shielded or the unshieldedsources using conventional quarter and half-wave rf configurationsproduce undesirable results.

[0017] In many conventional plasma sources a means of cooling isrequired to maintain the plasma source and substrates being treatedbelow a maximum temperature limit. Power dissipation in the structurecauses heating and thereby increases the difficulty and expense ofimplementing effective cooling means. Inductive currents may also becoupled from the excitation coil into internal or capacitive shields andthese currents are an additional source of undesirable power loss andheating. Conventional capacitive shielding in helical resonatordischarges utilized a shield which was substantially split along thelong axis of the resonator to lessen eddy current loss. However, such ashield substantially perturbs the resonator characteristics owing tounwanted capacitive coupling and current which flows from the coil tothe shield. Since there are no general design equations, nor areproperties currently known for resonators which are “loaded” with ashield along the axis, sources using this design must be sized and madeto work by trial and error.

[0018] In inductive discharges, it is highly desirable to be able tosubstantially control the plasma potential relative to ground potential,independent of input power, pressure, gas composition and othervariables. In many cases, it is desired to have the plasma potential besubstantially at ground potential (or at least offset from groundpotential by an amount insignificantly different from the floatingpotential or intrinsic DC plasma potential). For example, when a plasmasource is utilized to generate neutral species to be transporteddownstream of the source for use in ashing resist on a semiconductordevice substrate (a wafer or flat panel electronic display), theconcentration and potential of charged plasma species in the reactionzone are desirably reduced to avoid charging damage from electron orionic current from the plasma to the device. When there is a substantialpotential difference between plasma in the source and grounded surfacesbeyond the source, there is a tendency for unwanted parasitic plasmadischarges to form outside of the source region.

[0019] Another undesirable effect of potential difference is theacceleration of ions toward grounded surfaces and subsequent impact ofthe energetic ions with surfaces. High energy ion bombardment may causelattice damage to the device substrate being processed and may cause thechamber wall or other chamber materials to sputter and contaminatedevice wafers. In other plasma processing procedures, however, some ionbombardment may be necessary or desirable, as is the case particularlyfor anisotropic ion-induced plasma etching procedures (for a discussionof ion-enhanced plasma etching mechanisms See Flamm (Ch. 2, pp.94-183 inPlasma Etching, An Introduction, D. M. Manos and D. L. Flamm, eds.,Academic Press, 1989)). Consequently, uncontrolled potentialdifferences, such as that caused by “stray” capacitive coupling from thecoil of an inductive plasma source to the plasma, are undesirable.

[0020] Referring to the above limitations, conventional plasma sourcesalso have disadvantages when used in conventional plasma enhanced CVDtechniques. These techniques commonly form a reaction of a gascomposition in a plasma discharge. One conventional plasma enhancedtechnique relies upon ions aiding in rearranging and stabilizing thefilm, provided the bombardment from the plasma is not sufficientlyenergetic to damage the underlying substrate or the growing film.Conventional resonators and other types of inductive discharges oftenproduce parasitic plasma currents from capacitive coupling, which oftendetrimentally influence film quality, e.g., an inferior film, etc. Theseparasitic plasma currents are often uncontrollable, and highlyundesirable. These plasma sources also have disadvantages in otherplasma processing techniques such as ion-assisted etching, and others.Of course, the particular disadvantage will often depend upon theapplication.

[0021] To clarify certain concepts used in this application, it will beconvenient to introduce these definitions.

[0022] Ground (or ground potential): These terms are defined as areference potential which is generally taken as the potential of ahighly conductive shield or other highly conductive surface whichsurrounds the plasma source. To be a true ground shield in the sense ofthis definition, the RF conductance at the operating frequency is oftensubstantially high so that potential differences generated by currentwithin the shield are of negligible magnitude compared to potentialsintentionally applied to the various structures and elements of theplasma source or substrate support assembly. However, some realizationsof plasma sources do not incorporate a shield or surface with adequateelectrical susceptance to meet this definition. In implementations wherethere is a surrounding conductive surface that is somewhat similar to aground shield or ground plane, the ground potential is taken to be thefictitious potential which the imperfect grounded surface would haveequilibrated to if it had zero high frequency impedance. In designswhere there is no physical surface which is adequately configured orwhich does not have insufficient susceptance to act as a “ground”according to the above definition, ground potential is the potential ofa fictitious surface which is equi-potential with the shield or “ground”conductor of an unbalanced transmission line connection to the plasmasource at its RF feed point. In designs where the plasma source isconnected to an RF generator with a balanced transmission line RF feed,“ground” potential is the average of the driven feed line potentials atthe point where the feed lines are coupled to the plasma source.

[0023] Inductively Coupled Power: This term is defined as powertransferred to the plasma substantially by means of a time-varyingmagnetic flux which is induced within the volume containing the plasmasource. A time-varying magnetic flux induces an electromotive force inaccord with Maxwell's equations. This electromotive force induces motionby electrons and other charged particles in the plasma and therebyimparts energy to these particles.

[0024] RF inductive power source and bias power supply: In mostconventional inductive plasma source reactors, power is supplied to aninductive coupling element (the inductive coupling element is often amulti-turn coil which abuts a dielectric wall containing a gas where theplasma is ignited at low pressure) by an rf power generator. The chuckor workpiece support is often isolated from ground by a capacitance andpowered by a second rf power generator which is termed a bias powersupply. Rf power delivered to the chuck may cause the chuck to develop anegative DC bias voltage relative to plasma potential (for a discussionof bias, See Flamm (Ch. 1,pp.28-35, in Plasma Etching, An Introduction,D. M. Manos and D. L. Flamm, eds., Academic Press, 1989)). A bias powersource is often selected to operate at the same frequency as theinductive power source, however it can also operate at a distinctfrequency since the bias frequency can be adjusted to control ionbombardment energy, flux and other etching properties such asuniformity.

[0025] Vector sum voltage or current: Those skilled in the art willrecognize that alternating currents and voltages are often representedas complex numbers which are sometimes termed phasors (for a explanationof phasors see Ch. 10 in Electric Circuits, 2nd Ed., by J. W. Nilsson,Addison Wesley, 1986 ISBN 0-201-12695-8. Complex voltages and currentsare explained in Chapt. 8 of Electricity and Magnetism by E. M. Purcell,Berkeley Physics Course-Volume 2, McGraw-Hill, 1985, ISBN0-07-004908-4). The vector sum of two currents I₁ and I₂ or voltages V₁and V₂ is understood to be defined as the sum of these quantitiesexpressed as complex numbers (phasors) which contain both magnitude andphase information. At any particular time t, actual physical current isgiven by the real part of this complex sum.

[0026] Inverse voltage or current: Those skilled in the art willrecognize that two electrical quantities are said to be the inverse ofeach other when they have the same magnitude, but opposite sign. Henceif a voltage V₁ is given by V_(o)e^(jωt) its inverse is equal to−V_(o)e^(jωt) (or equivalently V_(o)e^(jωt±π)). Correspondingly thevector sum of any current summed with its inverse is zero.

[0027] Inverse phase or antiphase: Two electrical quantities are definedto have an inverse phase relationship when the phase difference betweenthem is 180° (π) or equivalently, (2n±1)π, where n is an integer number.It will be understood that two voltages or currents are in an inverserelationship when they have the same absolute magnitude and a phasedifference of (2n±1)π. However the sum of a first current added to asecond current characterized as having an inverse phase relation to thefirst (or equivalently “antiphase”) may not be zero, since the sum ofthese currents will balance to zero (the currents “compensate”) onlywhen both have the same magnitude.

[0028] Conventional Helical Resonator: Conventional helical resonatorcan be defined as plasma applicators. These plasma applicators have beendesigned and operated in multiple configurations, which were describedin, for example, U.S. Pat. No. 4,918,031 in the names of Flamm et al.,U.S. Pat. No. 4,368,092 in the name of Steinberg et al., U.S. Pat. No.5,304,282 in the name of Flamm, U.S. Pat. No. 5,234,529 in the name ofJohnson, U.S. Pat. No. 5,431,968 in the name of Miller, and others. Inthese configurations, one end of the helical resonator applicator coilhas been grounded to its outer shield. In one conventionalconfiguration, a quarter wavelength helical resonator section isemployed with one end of the applicator coil grounded and the other endfloating (i.e., open circuited). A trimming capacitance is sometimesconnected between the grounded outer shield and the coil to “fine tune”the quarter wave structure to a desired resonant frequency that is belowthe native resonant frequency without added capacitance. In anotherconventional configuration, a half-wavelength helical resonator sectionwas employed in which both ends of the coil were grounded. The functionof grounding the one or both ends of the coil was believed to be notessential, but advantageous to “stabilize the plasma operatingcharacteristics” and “reduce the possibility of coupling stray currentto nearby objects.” See U.S. Pat. No. 4,918,031.

[0029] Conventional resonators have also been constructed in othergeometrical configurations. For instance, the design of helicalresonators with a shield of square cross section is described in Zverevet al., IRE Transactions on Component Parts, pp. 99-110, Sept. 1961.Johnson (U.S. Pat. No. 5,234,529) teaches that one end of thecylindrical spiral coil in a conventional helical resonator may bedeformed into a planar spiral above the top surface of the plasmareactor tube. U.S. Pat. No. 5,241,245 in the names of Barnes et al.teach the use of conventional helical resonators in which the spiralcylindrical coil is entirely deformed into a planar spiral arrangementwith no helical coil component along the sidewalls of the plasma source(this geometry has often been referred to as a “transformer coupledplasma,” termed a TCP).

[0030] From the above it is seen that an improved technique, including amethod and apparatus, for plasma processing is often desired.

SUMMARY OF THE INVENTION

[0031] The present invention provides a technique, including a methodand apparatus, for fabricating a product using a plasma discharge. Thepresent technique relies upon the control of the instantaneous plasma ACpotential to selectively control a variety of plasma characteristics.These characteristics include the amount of reactive neutral species,the amount of charged species, time and spatially averaged plasmapotentials, the spatial extent and distribution of plasma density, thedistribution of electrical current, and others. This technique can beused in applications including chemical dry etching, ion-enhancedetching, plasma immersion ion implantation, chemical vapor depositionand material growth, and others.

[0032] In one aspect of the invention, a device is made using a processfor fabricating a product. These products include a varieties of devices(e.g., semiconductor, flat panel displays, micro-machined structures,etc.) and materials, e.g., diamonds, raw materials, plastics, etc. Theprocess includes steps of subjecting a substrate to a composition ofentities. At least one of the entities emanates from a species generatedby a gaseous discharge which is powered by high frequency fields coupledfrom an inductive coupling structure, in which the vector sum of phaseand inverse-phase capacitively coupled currents between the inductivecoupling structure and the gaseous plasma discharge can be selectivelyproduced or substantially balanced. The capacitively coupled currentsare driven by the AC voltage differences between the potential along theinductive coupling structure and the plasma potential. This processprovides for a technique that is substantially free from stray orparasitic capacitive coupling from the plasma source to chamber bodies(e.g., substrate, walls, etc.) at or near ground potential.

[0033] In another aspect of the invention, another method forfabricating a product is provided. The process includes steps ofsubjecting a substrate to a composition of entities. At least one of theentities emanates from a species generated by a gaseous discharge whichis powered by high frequency fields coupled from an inductive couplingstructure, in which the vector sum of phase and inverse-phase capacitivecoupled current from the inductive coupling structure is selectivelymaintained. In one embodiment of this method, a process provides for atechnique that can selectively control the amount of capacitive couplingto chamber bodies at or near ground potential. In a second embodiment,the process provides for a technique that can selectively control thepotential difference between the plasma and a product being processed.It will be evident to those skilled in the art that there is arelationship between the plasma potential and current. Thereforeselective control of the potential difference may advantageously be usedto control the amount of charge flowing to a product being processed.Merely by way of example, one such product might be a device wafer whichcan be damaged by excessive charge or ion bombardment energy.

[0034] In another aspect of the invention, a further method forfabricating a product is provided. The process includes steps ofsubjecting a substrate to a composition of entities. At least one of theentities emanates from a species generated by a gaseous discharge whichis powered by high frequency fields coupled from an inductive couplingstructure, in which the vector sum of phase and inverse-phase capacitivecoupled current from the inductive coupling structure is selectivelymaintained. In one aspect of this method, a process provides for atechnique that can selectively control the amount of capacitive couplingto chamber bodies at or near ground potential. In a second aspect, aprocess provides for a technique that can selectively control thepotential difference between the plasma and a product being processed.It will be evident to those skilled in the art that there is a directrelationship between current flow to the product and the differencebetween plasma potential and the product potential. Therefore selectivecontrol of the potential difference may advantageously be used tocontrol the amount of charge flowing to a product being processed.Merely by way of example, one such product might be a device wafer whichcan be damaged by excessive charge or ion bombardment energy.

[0035] An additional aspect of the invention, provides a further processfor fabricating a product. This process includes the steps of subjectinga substrate to a composition of entities wherein at least one of theentities emanates from a species generated by a gaseous discharge. Thegaseous discharge is powered by high frequency fields coupled from acoupling structure, in which the vector sum of phase and inverse-phasecapacitive coupled currents from the inductive coupling structure areselectively maintained. A further step of selectively applying a voltagebetween the at least one of the entities in the plasma source and asubstrate is provided. Yet a further step provides for sensing thecurrent flow to a substrate and using selectively maintained voltagedifferences between the substrate and at least one of the entities inthe plasma source to control the current flow.

[0036] Another aspect of the invention provides another process forfabricating a product. The process comprises steps of subjecting asubstrate to a composition of entities and using the resulting substratefor completion of the product. At least one of the entities emanatesfrom a species generated by a gaseous discharge provided by a plasmaapplicator, e.g., a helical resonator, inductive coil, transmissionline, etc. This plasma applicator has an integral current flow to theplasma driven by capacitive coupling of a plasma column to elements witha selected potential greater than a surrounding shield potentialsubstantially equal to capacitive coupling of the plasma column tosubstantially equal elements with a potential below shield potential.

[0037] In a further aspect, the invention provides an apparatus forfabricating a product. The apparatus has an enclosure comprising anouter surface and an inner surface. The enclosure houses a gaseousdischarge. The apparatus also includes a plasma applicator (e.g.,helical coil, inductive coil, transmission line, etc.) disposed adjacentto the outer surface. A high frequency power source operably coupled tothe plasma applicator is included. The high frequency power sourceprovides power to excite the gaseous discharge to provide at least oneentity from a high frequency field in which the vector sum of phase andinverse-phase capacitive currents coupled from the inductive couplingstructure is selectively maintained.

[0038] In another aspect, the present invention provides an improvedplasma discharge apparatus. This plasma discharge apparatus includes aplasma source, a plasma applicator (e.g., inductive coil, transmissionline, etc.), and other elements. This plasma applicator provides ade-coupled plasma source. A wave adjustment circuit (e.g., RLC circuit,coil, transmission line, etc.) is operably coupled to the plasmaapplicator structure. The wave adjustment circuit can selectively adjustphase and inverse-phase potentials between the plasma and applicatorelements, produced by at least one rf power supply. The rf power supply(or supplies) are operably coupled to the wave adjustment circuit.

[0039] The present invention achieves these benefits in the context ofknown process technology. However, a further understanding of the natureand advantages of the present invention may be realized by reference tothe latter portions of the specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040]FIG. 1 is a simplified diagram of a plasma etching apparatusaccording to the present invention;

[0041] FIGS. 2A-2E are simplified configurations using wave adjustmentcircuits according to the present invention;

[0042]FIG. 3 is a simplified diagram of a chemical vapor depositionapparatus according to the present invention;

[0043]FIG. 4 is a simplified diagram of a stripper according to thepresent invention;

[0044] FIGS. 5A-5C are more detailed simplified diagrams of a helicalresonator according to the present invention;

[0045]FIG. 6 is a conventional quarter-wave helical resonator plasmaetching apparatus with stray plasma which results from the coupling inthe conventional design;

[0046]FIG. 7 is a simplified diagram of the rf voltage distributionalong the coil of the FIG. 6 apparatus;

[0047]FIG. 8 is a simplified top-view diagram of an apparatus suitablefor CDE or resist ashing apparatus according to the present examples;and

[0048]FIG. 9 is a simplified side-view diagram of a chamber suitable forCDE or resist ashing chamber according to the present examples.

DETAILED DESCRIPTION OF THE INVENTION

[0049]FIG. 1 is a simplified diagram of a plasma etch apparatus 10according to the present invention. This etch apparatus is provided withan inductive applicator, e.g., inductive coil. This etch apparatusdepicted, however, is merely an illustration, and should not limit thescope of the claims as defined herein. One of ordinary skilled in theart may implement the present invention with other treatment chambersand the like.

[0050] The etch apparatus includes a chamber 12, a feed source 14, anexhaust 16, a pedestal 18, an inductive applicator 20, a radio frequency(rf) power source 22 to the inductive applicator 20, wave adjustmentcircuits 24, 29 (WACs), a radio frequency power source 35 to thepedestal 18, a controller 36, and other elements. Optionally, the etchapparatus includes a gas distributor 17.

[0051] The chamber 12 can be any suitable chamber capable of housing aproduct 28, such as a wafer to be etched, and for providing a plasmadischarge therein. The chamber can be a domed chamber for providing auniform plasma distribution over the product 28 to be etched, but thechamber also can be configured in other shapes or geometries, e.g., flatceiling, truncated pyramid, cylindrical, rectangular, etc. Dependingupon the application, the chamber is selected to produce a uniformentity density over the pedestal 18, providing a high density ofentities (i.e., etchant species) for etching uniformity.

[0052] The present chamber includes a dome 25 having an interior surface26 made of quartz or other suitable materials. The exterior surface ofthe chamber is typically a dielectric material such as a ceramic or thelike. Chamber 12 also includes a process kit with a focus ring 32, acover (not shown), and other elements. Preferably, the plasma dischargeis derived from the inductively coupled plasma source that is ade-coupled plasma source (DPS) or a helical resonator, although othersources can be employed.

[0053] The de-coupled source originates from rf power derived from theinductive applicator 20. Inductively coupled power is derived from thepower source 22. The rf signal frequencies ranging from 800 KHz to 80MHz can be provided to the inductive applicator 20. Preferably, the rfsignal frequencies range from 5 MHz to 60 MHz. The inductive applicator(e.g., coil, antenna, transmission line, etc.) overlying the chamberceiling can be made using a variety of shapes and ranges of shapes. Forexample, the inductive applicator can be a single integral conductivefilm, a transmission line, or multiple coil windings. The shape of theinductive applicator and its location relative to the chamber areselected to provide a plasma overlying the pedestal to improve etchuniformity.

[0054] The plasma discharge (or plasma source) is derived from theinductive applicator 20 operating at selected phase 23 and inverse-phase27 potentials (i.e., voltages) that substantially cancel each other. Thecontroller 36 is operably coupled to the wave adjustment circuits 24,29. In one embodiment, wave adjustment circuits 24, 29 provide aninductive applicator operating at full-wave multiples 21. Thisembodiment of full-wave multiple operation provides for balancedcapacitive coupling to of the plasma to phase 23 and inverse-phasevoltages 27 along the inductive applicator (or coil adjacent to theplasma). This full-wave multiple operation reduces or substantiallyeliminates the amount of capacitively coupled power from the plasmasource to chamber bodies (e.g., pedestal, walls, wafer, etc.) at orclose to ground potential. Alternatively, the wave adjustment circuits24, 29 provide an inductive applicator that is effectively made shorteror longer than a full-wave length multiple by a selected amount, therebyoperating with coupling to selected phase and inverse-phase voltageswhich do not comprise full-wave multiples. Alternatively, more than two,one or even no wave adjustment circuits can be provided in otherembodiments. But in all of these above embodiments, the coupling tophase and inverse-phase potentials substantially cancel each other,thereby providing substantially no capacitively coupled power from theplasma source to the chamber bodies.

[0055] In alternative embodiments, the wave adjustment circuit can beconfigured to provide selected phase and inverse-phase voltages coupledfrom the inductive applicator to the plasma that do not cancel. Thisprovides a controlled potential between the plasma and the chamberbodies, e.g., the substrate, grounded surfaces, walls, etc. In oneembodiment, the wave adjustment circuits can be used to selectivelyreduce current (i.e., capacitively coupled current) to the plasma. Thiscan occur when certain high potential difference regions of theinductive applicator to the plasma are positioned (or kept) away fromthe plasma region (or inductor-containing-the-plasma region) by makingthem go into the wafer adjustment circuit assemblies, which aretypically configured outside of the plasma region. In this embodiment,capacitive current is reduced and a selected degree of symmetry betweenthe phase and inverse-phase of the coupled voltages is maintained,thereby providing a selected potential or even substantially groundpotential. In other embodiments, the wave adjustment circuits can beused to selectively increase current (i.e., capacitively coupledcurrent) to the plasma.

[0056] As shown, the wave adjustment circuits are attached (e.g.,connected, coupled, etc.) to ends of the inductive applicator.Alternatively, each of these wave adjustment circuits can be attached atan intermediate position away from the inductive application ends.Accordingly, upper and lower tap positions for respective waveadjustment circuits can be adjustable. But both the inductive applicatorportions below and above each tap position are active. That is, theyboth can interact with the plasma discharge.

[0057] A sensing apparatus can be used to sense plasma voltage and useautomatic tuning of the wave adjustment circuits and any rf matchingcircuit between the rf generator and the plasma treatment chamber. Thissensing apparatus can maintain the average AC potential at zero or aselected value relative to ground or any other reference value. Thiswave adjustment circuit provides for a selected potential differencebetween the plasma source and chamber bodies. These chamber bodies maybe at a ground potential or a potential supplied by another bias supply,e.g., See FIG. 1 reference numeral 35. Examples of wave adjustmentcircuits are described by way of the Figs. below.

[0058] For instance, FIGS. 2A to 2E are simplified configurations usingthe wave adjustment circuits according to the present invention. Thesesimplified configurations should not limit the scope of the claimsherein. In an embodiment, these wave adjustment circuits employsubstantially equal circuit elements (e.g., inductors, capacitors,transmission line sections, and others) such that the electrical lengthof the wave adjustment circuits in series with the inductive applicatorcoupling power to the plasma is substantially an integral multiple ofone wavelength. In other embodiments, the circuit elements provide forinductive applicators at other wavelength multiples, e.g.,one-sixteenth-wave, one-eighth-wave, quarter-wave, half-wave,three-quarter wave, etc. In these embodiments (e.g., full-wave multiple,half-wave, quarter-wave, etc.), the phase and inverse-phase relationshipbetween the potentials coupled to the plasma substantially cancel eachother. In further embodiments, the wave adjustment circuits employcircuit elements that provide plasma applicators with phase andinverse-phase potential relationships that do not cancel each other outusing a variety of wave length portions.

[0059]FIG. 2A is a simplified illustration of an embodiment 50 usingwave adjustment circuits according to the present invention. Thisembodiment 50 includes a discharge tube 52, an inductive applicator 55,an exterior shield 54, an upper wave adjustment circuit 57, a lower waveadjustment circuit 59, an rf power supply 61, and other elements. Theupper wave adjustment circuit 57 is a helical coil transmission lineportion 69, outside of the plasma source region 60. Lower waveadjustment circuit 59 also is a helical coil transmission line portion67 outside of the plasma source region 60. The power supply 61 isattached 65 to this lower helical coil portion 67, and is grounded 63.Each of the wave adjustment circuits also are shielded 66, 68.

[0060] In this embodiment, the wave adjustment circuits are adjusted toprovide substantially zero AC voltage at one point on the inductive coil(refer to point 00 in FIG. 2A). This embodiment also providessubstantially equal phase 70 and inverse-phase 71 voltage distributionsin directions about this point (refer to 00-A and 00-C in FIG. 2A) andprovides substantially equal capacitance coupling to the plasma fromphysical inductor elements (00-C) and (00-A), carrying the phase andinverse-phase potentials. Voltage distributions 00-A and 00-C arecombined with C-D and A-B (shown by the phantom lines) wouldsubstantially comprise a full-wave voltage distribution in thisembodiment where the desired configuration is a selectedphase/inverse-phase portion of a full-wave inductor (or helicalresonator) surrounding the plasma source discharge tube.

[0061] In this embodiment, it is desirable to reduce or minimizecapacitive coupling current from the inductive element to the plasmadischarge in the plasma source. Since the capacitive current increasesmonotonically with the magnitude of the difference of peak phase andinverse-phase voltages, which occur at points A and C in FIG. 2A, thiscoupling can be lessened by reducing this voltage difference. In FIG.2A, for example, it is achieved by way of two wave adjustment circuits57, 59. Coil 55 (or discharge source) is a helical resonator and thewave adjustment circuits 57, 59 are helical resonators.

[0062] The discharge source helical resonator 53 can be constructedusing conventional design formulae. Generally, this helical resonatorincludes an electrical length which is a selected phase portion “x” (Ato 00 to C) of a full-wave helical resonator. The helical resonator waveadjustment circuits are each selected to comprise a portion (2n-x) offull-wave helical resonators. Physical parameters for the waveadjustment helical resonators can be selected to realize practicalphysical dimensions and appropriate Q, Z₀, etc. values. In particular,some or even all of the transmission line parameters (Q, Z₀, etc.) ofthe wave adjustment circuit sections may be selected to be substantiallythe same as the transmission line parameters of the inductiveapplicator. The portion of the inductive plasma applicator helicalresonator, on the other hand, is designed and sized to provide selecteduniformity values over substrate dimensions within an economicalequipment size and reduced Q.

[0063] The wave adjustment circuit provides for external rf powercoupling, which can be used to control and match power to the plasmasource, as compared to conventional techniques used in helicalresonators and the like. In particular, conventional techniques oftenmatch to, couple power to, or match to the impedance of the power supplyto the helical resonator by varying a tap position along the coil abovethe grounded position, or selecting a fixed tap position relative to agrounded coil end and matching to the impedance at this position using aconventional matching network, e.g., LC networks network, etc. Varyingthis tap position along the coil within a plasma source is oftencumbersome and generally imposes difficult mechanical design problems.Using the fixed tap and external matching network also is cumbersome andcan cause unanticipated changes in the discharge Q, and thereforeinfluences its operating mode and stability. In the present embodiments,the wave adjustment circuits can be positioned outside of the plasmasource (or constrained in space containing the inductive coil, e.g., SeeFIG. 2A. Accordingly, the mechanical design (e.g., means for varying tapposition, change in the effective rf power coupling point by electricalmeans, etc.) of the tap position are simplified relative to thoseconventional techniques.

[0064] In the present embodiment, rf power is fed into the lower waveadjustment circuit 59. Alternatively, rf power can be fed into the upperwave adjustment circuit (not shown). The rf power also can be coupleddirectly into the inductive plasma coupling applicator (e.g., coil,etc.) in the wave adjustment circuit design, as illustrated by FIG. 2B.Alternatively, other application will use a single wave adjustmentcircuit, as illustrated by FIG. 2C. Power can be coupled into this waveadjustment circuit or by conventional techniques such as a tap in thecoil phase. In some embodiments, this tap in the coil phase ispositioned above the grounded end. An external impedance matchingnetwork may then be operably coupled to the power for satisfactory powertransfer efficiency from, for example, a conventional coaxial cable toimpedances (current to voltage rations) existing between the waveadjustment circuit terminated end of the applicator.

[0065] A further embodiment using multiple inductive plasma applicatorsalso is provided, as shown in FIG. 2D. This embodiment includes multipleplasma applicators (PA1, PA2 . . . Pan). These plasma applicatorsrespectively provide selected combinations of inductively coupled powerand capacitively coupled power from respective voltage potentials (V1,V2 . . . Vn). Each of these plasma applicators derives power from itspower source (PS1, PS2 . . . PSn) either directly through an appropriatematching or coupling network or by coupling to a wave adjustment circuitas described. Alternatively, a single power supply using power splittersand impedance matching networks can be coupled to each (or more thantwo) of the plasma applicators. Alternatively, more than one powersupply can be used where at least one power supply is shared among morethan one plasma applicator. Each power source is coupled to itsrespective wave adjustment circuits (WAC1, WAC2 . . . WACn).

[0066] Generally, each plasma applicator has an upper wave adjustmentcircuit (e.g., WAC 1a, WAC 2a . . . WAC na) and a lower wave adjustmentcircuit (e.g., WAC1b, WAC 2b . . . WACnb). The combination of upper andlower wave adjustment circuits are used to adjust the plasma sourcepotential for each plasma source zone. Alternatively, a single waveadjustment circuit can be used for each plasma applicator. Each waveadjustment circuit can provide substantially the same impedancecharacteristics, or substantially distinct impedance characteristics. Ofcourse, the particular configuration used will depend upon theapplication.

[0067] For instance, multiple plasma applicators can be used to employdistinct excitation frequencies for selected zones in a variety ofapplications. These applications include film deposition using plasmaenhanced chemical deposition, etching by way of ion enhanced etching orchemical dry etching and others. Plasma cleaning also can be performedby way of the multiple plasma applicators. Specifically, at least one ofthe plasma applicators will define a cleaning plasma used for cleaningpurposes. In one embodiment, this cleaning plasma can have an oxygencontaining species. This cleaning plasma is defined by using an oxygendischarge, which is sustained by microwave power to a cavity or resonantmicrowave chamber abutting or surrounding a conventional dielectricvessel. Of course, a variety of other processes also can be performed byway of this multiple plasma applicator embodiment.

[0068] This present application using multiple plasma applicators canprovide a multi-zone (or multi-chamber) plasma source without the use ofconventional mechanical separation means (e.g., baffles, separateprocess chambers, etc.). Alternatively, the degree of interactionbetween adjacent zones or chambers can be relaxed owing to the use ofvoltage potential control via wave adjustment circuits. This plasmasource provides for multiple plasma source chambers, each with its owncontrol via its own plasma applicator. Accordingly, each plasmaapplicator provides a physical zone region (i.e., plasma source) withselected plasma characteristics (e.g., capacitively coupled current,inductively coupled current, etc.). These zones can be used alone or canbe combined with other zones. Of course, the particular configurationwill depend upon the application.

[0069] In the present embodiments, the wave adjustment circuit can bemade from any suitable combination of element(s) such as various typesof transmission lines, circuits, etc. These transmission lines includeconventional solid or air dielectric coaxial cable, or ordinary,repeating inductor/capacitor discrete approximations to transmissionlines, and others. These types of transmission lines are coaxialtransmission lines, balanced parallel transmission lines, so called slowwave transmission lines with a spiral inner conductor (e.g., selectedportions of a helical resonator, etc.), and others. Individual lumped,fixed, or adjustable combinations of resistors, capacitors, andinductors (e.g., matching networks, etc.) also can be used in place oftransmission line sections for the wave adjustment circuit. Thesegeneral types of wave adjustment circuits are frequency dependent, andcan be termed frequency dependent wave adjustment circuits (or FDWACs).

[0070] Frequency independent elements also can be used as the waveadjustment circuits. These wave adjustment circuits can be termedfrequency independent WACs (or FIWACs). Frequency independent waveadjustment circuits include degenerate cases such as short-circuitconnections to ground or an infinite impedance (i.e., open circuit), andothers. Frequency independent wave adjustment circuits can be usedalone, or in combination with the frequency dependent wave adjustmentcircuits. Alternatively, the frequency dependent wave adjustmentcircuits can be used alone or in combination with other wave adjustmentcircuits. Other variations, alternative constructions, and modificationsalso may be possible depending upon the application.

[0071] With regard to operation of the wave adjustment circuits, variousembodiments can be used, as illustrated by FIG. 2E. The wave adjustmentcircuits are used to select a wave length portion to be applied in theplasma applicator. In some embodiments, the average rf plasma potentialis maintained close to ground potential by providing substantially equalphase 90, 81 and inverse-phase 91, 82 capacitively coupled portions ofthe inductive applicator. This can occur in multi-wave embodiments 92,full-wave embodiments 93, half-wave multiple embodiments, quarter-wavemultiple embodiments, or any other embodiments 94.

[0072] In alternative embodiments, it is desirable to maintain anelevated source plasma voltage relative to ground potential to induce acontrolled ion plasma flux (or ion bombardment) to the product substrate(or any other chamber bodies). These embodiments are provided byselecting distinct electrical lengths for each of the wave adjustmentcircuit sections such that the capacitive coupled current from a phasesection of the inductive plasma applicator is in excess of capacitivecoupled current from its inverse-phase portion. In these embodiments,the wave adjustment circuit provides a deliberate imbalance betweencoupling to phase and inverse-phase voltages. In some embodiments 97,this occurs by shifting the zero voltage nodes along the process chamberaxially, thereby achieving a bias relative to the plasma discharge. Asshown, the phase 95 is imbalanced relative to its inverse-phase 96. Inother embodiments 99, one phase portion 84 is imbalanced by way of adifferent period relative to its complementary phase portion 85. Otherembodiments are provided where the source plasma voltage is lowerrelative to ground potential. In the embodiments were imbalance isdesirable, the potential difference between the phase and inverse-phasepotential portions is reduced (or minimized) when the amount ofsputtering (e.g., wall sputtering, etc.) is reduced. The amount ofsputtering, however, can be increased (or maximized) by increasing thepotential difference between the phase and inverse-phase potentialportions. Sputtering is desirable in, for example, sputtering a quartztarget, cleaning applications, and others. Of course, the type ofoperation used will depend upon the application..

[0073] Current maxima on an inductive applicator with distributedcapacitance (e.g., helical resonator transmission line, etc.) occur atvoltage minima. In particular, conventional quarter-wave helicalresonator current is substantially at a relative maximum at its groundedend of the coil, and to a lesser extend in the nearby coil elements.Therefore, partial inductive coupling of power, if it occurs, will tendto be at this grounded end. In conventional half-wave helicalresonators, inductive coupling tends to occur at each of the twogrounded ends.

[0074] In the present invention, substantially equal coupling to voltageelements and inverse-voltage elements along half-wave and otherfractional wave inductive applicator structure sections supportsubstantially more inductive coupling at a selected rf voltage node,e.g., FIG. 2A reference numeral 00. This effect is caused by highcurrent flow in the inductor applicator zones (or sections) bothdirectly above and below the node (corresponding to inductor elements inthe phase and inverse-phase sections at and immediately adjacent to therf voltage zero point). It should be noted that conventional quarter andhalf-wave inductively coupled inductive applicators have inductivecoupling which abruptly declines below the grounded coil locationsbecause the coil terminates and voltage extrema are present at theselocations. This generally produces conventional quarter and half-wavehelical resonators that tend to operate in a capacitive mode, or with asubstantial fraction of power which is capacitively coupled to theplasma, unless the plasma is shielded from coil voltages, as notedabove.

[0075] In a specific embodiment, the power system includes selectedcircuit elements for effective operation. The power system includes anrf power source. This rf power source can be any suitable rf generatorcapable of providing a selected or continuously variable frequency in arange from about 800 kHz to about 80 MHz. Many generators are useful.Preferably, generators capable of operating into short and open-circuitloads without damage are used for industrial applications. One exampleof a suitable generator is a fixed frequency rf generator 28.12 MHz-3 kWCX-3000 power supply made by Comdel, Inc. of Beverly, Mass. A suitablevariable frequency power supply arrangement capable of the 3 kW outputover an 800 kHz to 50 MHz range can be made by driving an IFI ModelTCCX3500 High Power Wide Band Amplifier with a Hewlett Packard HP116A,0-50 Mhz Pulse/Function Generator. Other generators including thosecapable of higher or lower power also can be used depending upon theapplication.

[0076] Power from the generator can be transmitted to the plasma sourceby conventional coaxial cable transmission line. An example of thistransmission line is RG8/U and other higher temperature rated cable(e.g., RG1151U, etc.) with a coaxial TEFLON™ dielectric. In someembodiments, power is fed to conventional end-grounded half-wave helicalresonators by positioning a movable tap on the helical coil andconnecting a power source between the tap and the ground. In otherembodiments, matching networks can be introduced between the coaxialcable power feed and the, helical coil tap for flexibility. The matchingnetwork will depend on the selected wave configuration and waveadjustment circuits. In a balanced half-wave helical resonatorembodiment, for example, the ends of the resonator coil can beterminated with wave adjustment circuits which substantially have zerosusceptance. In particular, the wave adjustment circuit is designed asan open circuit by making no electrical connections to the ends of thecoil, or establishing an electrical equivalence thereof. Alternatively,the ends of the coil are isolated by high series impedance chokes,thereby maintaining DC coupling to a fixed reference potential. Thesetypes of wave adjustment circuits are frequency independent and are“degenerate” cases. In these embodiments, the rf power is provided suchthat the phase and inverse-phase current flows above and below theelectrical midpoint (i.e., zero voltage node, etc.) of the coil. Thisprovides for substantially balanced phase and inverse-phase current flowfrom the power source stabilizing desired operation in coil voltagesabove the midpoint of the coil, and also provides substantially equalphase and inverse-phase voltages.

[0077] The embodiments described above also can be applied to otherplasma processing applications, e.g., PECVD, plasma immersion ionimplantation (PIII), stripping, sputtering, etc. For instance, FIG. 3 isa simplified CVD apparatus 100 according to the present invention. Thepresent CVD apparatus includes a chamber 112, a feed source 114, anexhaust 116, a pedestal 118, a power source 122, a ground 124, a helicalresonator 126, and other elements. The helical resonator 126 has a coil132, an outer shield 133, and other elements. The chamber can be anysuitable chamber capable of housing a product 119 such as a wafer fordeposition, and for providing a plasma discharge therein. Preferably,the chamber is a right circular cylinder chamber for providing anuniform plasma species distribution over the product. But the chambercan also be configured in the form of rectangular right cylinder, atruncated cone, and the like. The chamber and fixtures are constructedfrom aluminum and quartz, and other suitable materials. The plasmadischarge is derived from a plasma source which is preferably a helicalresonator discharge or other inductive discharge using a wave adjustmentcircuit or other techniques to selectively adjust phase/inverse-phasepotentials. The present CVD apparatus provides for deposition of adielectric material, e.g., silicon dioxide or the like.

[0078] The product 119 having an upper surface 130 is placed into thepresent CVD apparatus for deposition, e.g., plasma enhanced chemicalvapor deposition (PECVD), and others. Examples of deposition materialsinclude a dielectric material such as a silicon dioxide (SiO₂), aphosphosilicate glass (PSG), a borophosphosilicate glass (BPSG), asilicon nitride (Si₃N₄), among others.

[0079] In one embodiment, the deposition occurs by introducing a mixturecomprising organic silane, oxygen, and an inert gas such as helium orargon according to the present invention. The organic silane can be anysuitable organic silicate material such TEOS, HMDS, OMCTS, and the like.Deposition is also conformal in selected instances. As for the oxygen,it includes a flow rate of about 1 liter/per minute and less. A relativeflow rate between the organic silane such as TEOS and oxygen ranges fromabout 1:40 to about 2:1, and is preferably less than about 1:2 incertain applications. A deposition temperature of the organicsilane-oxygen layer ranges from about 300 to about 500° C., and can alsobe at other temperatures. Pressures in the range of 1 to 7 Torr aregenerally used. Of course, other concentrations, temperatures,materials, and flow rates can be used depending upon the particularapplication.

[0080] This chamber also includes a wave adjustment circuit 127. Thewave adjustment circuit 127 is used to provide a helical coil operatingwith capacitive coupling to selected phase and inverse-phase voltages.This portion 127 of the wave adjustment circuit coil also is shielded140 to prevent rf from interfering with the plasma discharge or externalelements, e.g., equipment, power, etc. The coil shield 140 is made of aconductive material such as copper, aluminum, or the like. In oneembodiment, an operating frequency is selected and the wave adjustmentcircuit is adjusted to short circuit the upper end of the helicalapplicator coil to ground 124. This provides a helical coil operating atapproximately a full-wave multiple and has substantially equal phase andinverse-phase sections. This full-wave multiple operation provides forbalanced capacitance of phase 151 and antiphase 153 voltages along thecoil 132 adjacent to the plasma source. Full-wave multiple operationreduces or even substantially eliminates the amount of capacitivelycoupled power from the plasma source to chamber bodies (e.g., pedestal,walls, wafer, etc.) at or close to ground potential.

[0081] In the present embodiment, the wave adjustment circuit 127 is avariable coil portion 128 of a spiral transmission line, which isselectively placed outside the outer shield 133. Accordingly, when thewave adjustment circuit is adjusted to become a short circuit, theplasma source “sees” only a selected full-wave multiple comprisingsubstantially equal phase 151 and anti-phase 153 of the entireinstantaneous AC voltages 134, 135. In this embodiment, stress of thedeposited oxide film is often tensile, which can be undesirable.

[0082] Alternatively, the wave adjustment circuit 127 provides a helicalresonator operating at selected phase and anti-phase voltages that arenot full-wave multiples. This wave adjustment circuit provides for aselected amount of capacitive coupling from the plasma source to thechamber bodies. Stress of the deposited oxide film in this embodimentcan be made to be zero or slightly compressive. In some embodiments, theoxide films can be deposed with an rf plasma potential of severalhundred volts between the plasma source and the substrate to decreasethe tendency of the oxide film to absorb moisture. This can occur byadjusting the wave adjustment circuit to add in a small section oftransmission line outside of the source and correspondingly shorteningthe applicator coil (by moving the lower point at which the applicatorcoil is short-circuited and thereby decreasing the inductance of theapplicator coil and electrical length of the helical resonator 126(e.g., spiral transmission line, etc.)). Of course, the selected amountof capacitive coupling will depend upon the application.

[0083]FIG. 4 is a simplified diagram of a resist stripper according tothe present invention. The present stripping apparatus includes similarelements as the previous described CVD apparatus. The present strippingapparatus includes a chamber 112, a feed source 114, an exhaust 116, apedestal 118, an rf power source 122, a ground 124, a helical resonator126, and other elements. The helical resonator 126 includes a coil 132,an outer shield 133, a wave adjustment circuit 400, and other elements.The chamber can be any suitable chamber capable of housing a product 119such as a photoresist coated wafer for stripping, and for providing aplasma discharge therein. The plasma discharge is derived from a plasmasource, which is preferably a helical resonator discharge or otherinductive discharge using a wave adjustment circuit or other techniquesto selectively adjust phase/anti-phase potentials. The present strippingapparatus provides for stripping or ashing photoresist, e.g., implanthardened, etc. Further examples of such a stripping apparatus aredescribed in the experiments section below.

[0084] In this embodiment, the wave adjustment circuits rely upon opencircuits (i.e., zero susceptance). Power transfer can be effected with abalanced feed such as an inductively-coupled push-pull arrangement withmeans such as coupled inductors. Techniques for constructing thesecoupled inductors are described in, for example, “The ARRL AntennaBook,” R. D. Straw, Editor, The American Radio Relay League, Newington,Conn. (1994) and “The Radio Handbook,” W. I. Orr, Editor, EngineeringLtd, Ind. (1962), which are both hereby incorporated by reference forall purposes. In one embodiment, a ferrite or powdered iron core “balun”(balanced-unbalanced) toroidal transformer (i.e., broadband transmissiontransformer, broadband transformer, etc.) 401 can be used to providebalanced matching from a conventional unbalanced coaxial transmissionline. Techniques for constructing toroidal baluns are described in, forexample, “Transmission Line Transformers,” J. Sevick, 2nd Edition,American Radio Relay League, Newington, Conn. (1990). The toroidaltransformer is coupled between the rf power source 122 and the coil 132.The midpoint 406 between the phase 405 and anti-phase voltage on thecoil is effectively rf grounded, hence it may be convenient to directlyground this midpoint of the inductive application in some embodimentsfor stability. This permits alternate operation in which power may becoupled into the inductive applicator (e.g., coil, etc.) with aconventional unbalanced feed line tapped on one side of the center.Push-pull balanced coupling ignites the plasma more easily thanconventional unbalanced coil tap matching and generally is easier toadjust in selected applications.

[0085] Referring to the helical resonator embodiments operating atsubstantially equal phase and anti-phase potentials, FIG. 5A is asimplified diagram 200 of an equivalent circuit diagram of some of them.The diagram is merely an illustration and should not limit the scope ofthe claims herein. The equivalent circuit diagram includes a pluralityof rf power supplies (V₁, V₂, V₃ . . . V_(n)) 203, representing forexample, a single rf power source. These power supplies are connected inparallel to each other. One end of the power supply is operably coupledto a ground connection 201. The other end of the power supplies can berepresented as being connected to a respective capacitor (C₁, C₂, C₃ . .. C_(n)). Each of these capacitors are connected in parallel to eachother. During this mode of operation, no significant voltage differenceexists between any of the common side of the capacitors, as they are allconnected to each other in parallel.

[0086]FIG. 5B is a simplified diagram of instantaneous AC voltage andcurrent along a helical resonator coil of FIG. 5A where each end of theinductive applicator is short circuited. The diagram is merely anillustration and should not limit the scope of the claims herein. Thisdiagram includes the discharge tube 213 and an inductive plasmadischarge (or plasma source) 501 therein. As shown, the plasma dischargeincludes an intensified “donut-shaped” glow region 501 that occupies alimited range (R) of the discharge tube 213. The plasma discharge has anaverage voltage potential (Vave) of magnitude that is substantiallywithin a few zero volts (i.e., the ground potential). As can be seen,the plasma discharge 501 has capacitively coupling elements to V_(H) andV_(G). But the average voltage potential of this plasma discharge issubstantially zero. This operation provides for balanced capacitance ofphase 503 and anti-phase 505 voltages along the coil adjacent to theplasma, thereby substantially preventing capacitively coupling from theplasma source to chamber bodies. As also shown, a current maxima 507exists at Vave, which corresponds to an inflection point between thephase 503 and the anti-phase 505.

[0087] In an alternative operating mode, dim rings of plasma caused byinductively coupled plasma current are visible near top and bottomextremes of the inductive application, as illustrated by FIG. 5C. Thisoperating mode is generally for a full-wave 517 inductive coupling coilwith a voltage distribution 518 and current distribution 519 operated ata very high power, e.g., maximum power input to the inductive applicatoris often limited by thermal considerations and breakdown. A full wavehelical resonator applicator 523 and rf feed 524 are shown in phantomalong the outside of a dielectric tube 532 enclosing the plasma. Therings 513, 515 of current in the plasma discharge are simulated bymaximum coil current areas corresponding to voltage minima at the centerof the coil as well as the top and bottom shorted ends of the coil.Under high power conditions, these subordinate current rings aredetectable and some excitation is often visible in the intermediateregions. This excitation is partially caused by capacitively drivencurrents within the discharge coupled to the voltage maximum and voltageminimum positions along the inductive applicator.

[0088] Alternatively, subordinate inductive plasma current rings at thetop and bottom ends 513 of the resonator do not appear with limitedinput power. The coil current and inductive flux fall beyond the ends ofthe inductive applicator so that a single inductive ring 515 in thecenter portion is more stable, provided that the conductivity of theplasma is large enough to support a single current ring at a specifiedinput power.

[0089] In alternative applications using high power operation, nosecondary plasma current rings may be desirable. These applicationsoften have substantially minimum internal capacitive coupling. In theseapplications, the inductive applicator (e.g., coil) abutting the vacuumvessel may be shortened from a full wave to an appropriate length suchthat only the central current maxima exists on the coil abutting theplasma source and the potential difference between maximum and minimumvoltage on the applicator is substantially reduced. The presentapplication is achieved by stabilizing the desired waveform along theapplicator by appropriate impedance wave adjustment circuits.

[0090] Referring to the above embodiments, the present inventionprovides for processing with an inductively coupled plasma in which theplasma potential from coupling to a phase portion of the inductiveapplicator is substantially not offset by capacitive coupling tocomplementary anti-phase voltages on selective portions of the inductivecoupling element. Conventional inductive sources (e.g., conventionalhelical resonators, etc.), however, have hitherto been operated inquarter-wave or half-wave modes. These modes substantially provide onlyphase capacitive coupling to the plasma, which raises the plasmapotential toward the coil in the absence of substantial anti-phasecompensation. Conventional inductive sources that are longer than ahalf-wave have been generally considered cumbersome and impractical forplasma reactors. In particular, these inductive sources are large insize, and have voltage nodes along the helical coil, which have beenbelieved to create a non-uniform plasma. In order to operate asubstantially inductive plasma in a helical resonator, conventionalinductive sources relied upon shielding the plasma tube from electricalfields originating on the coil. Shielding occurred, for example, byinserting a longitudinally split shield between the coil and plasmatube.

[0091] The present invention provides for a substantially pureinductively coupled power source. A benefit of this inductively coupledpower as a primary means to sustain plasma excitation is that electricfield lines produced by inductive coupling are purely rotational (e.g.they close on themselves). Hence they do not create or support a scalarpotential field (e.g. a voltage difference) within the plasma volume.Thus, in an ideal case, inductively coupled power can be transferredinto a plasma without no direct relationship between the plasmapotential and the voltages on coupling elements (e.g. the voltage on thecoil in a helical resonator) or voltages on rf matching networks, ifsuch are used. Furthermore, when transferring power to the plasma bypurely inductive means, power transfer does not require any significantpotential difference to be maintained between elements of the plasma andground potential (e.g. the potential difference between the plasma andground can be fixed by factors which are substantially independent ofinductive excitation power). Although in theory, inductive powertransfer does not require raising the AC or DC potential of the plasmawith respect to ground, in practice there has been substantial potentialshifts and harmful alteration in the plasma potential found inunshielded current art inductive sources.

[0092] As previously noted, and further emphasized herein, the mosteffective conventional method employed to avoid plasma potential shiftin conventional commercially available inductive sources is to shieldthe plasma from the electrical fields on the inductive coupling element(commonly a multi-turn coil) by inserting a grounded conductive memberbetween the inductive driving element and the plasma discharge tube.Shielding is, however, cumbersome and inconvenient and has seriousdisadvantages in practice. Shields couple to inductive applicatorelements and can cause wide excursions in the natural resonancefrequency, which are not predicted by conventional analytical designformulae. This often results in laborious trail and error and iterativemechanical designs to achieve a desired resonance. Another disadvantageof shielding is that shields often make it difficult to achieve initialignition of the plasma since shields generally exclude capacitiveelectric fields in the plasma discharge tube. In particular, ignition(known as plasma breakdown) of inductive breakdown generally begins witha capacitive electric field discharge, which is stable at lower currentsand powers See, for example, J. Amorim, H. S. Maciel and J. P. Sudana,J. Vac. Sci. Technol. B9, pp. 362-365, 1991). Accordingly, shields tendto block capacitive electric fields, which induce plasma ignition.

[0093] Insertion of the shield close to high voltage RF point in anetwork (such as the voltage maximum points in a helical resonator orthe high potential driven side of a TCP coil) also causes largedisplacement currents to flow through the capacitance between the shieldand coil. This high potential difference is also a potential cause ofdamaging rf breakdown across the air gap, hence the gap may requireprotection by inconvenient solid or liquid dielectric insulation. Thedisplacement current flow causes power loss and requires that higherpower RF generating equipment be used to compensate for the power loss.Coupling loss in the plasma source structure is also undesirable fromthe standpoint of thermal control. These limitations are overcome by thepresent invention using the wave adjustment circuits, an inductiveapplicator of selected phase length, and other elements.

EXAMPLES

[0094] To prove the principle and demonstrate the operation of thepresent invention, a helical resonator plasma source can be used in aphotoresist stripper for ashing with a pure O₂ plasma. A substantiallysimilar configuration is useful for chemical dry etching (CDE), asexemplified by the selective removal of silicon nitride over siliconoxide layers with a plasma sustained in feed gas mixtures containingsuitable mixtures of CF₄/O₂/N₂. Conventional helical resonators can alsobe evaluated. These are merely examples, and should not limit the scopeof the claims herein. One of ordinary skill in the art would easilyrecognize other examples, uses, variations, and modifications of theinventions defined by the claims.

[0095] I. Conventional Photoresist Stripper

[0096] In this example, a conventional quarter-wave helical resonatorresist stripper 600 can be constructed with a quarter-wave helicalresonator source 602 upstream of a processing chamber 604, shown in FIG.6. This quarter-wave helical resonator 602 included a coil 608 and otherelements.

[0097] Coil 608 consisted of 5.15 turns of 0.4 inch diameter coppertubing wound with a pitch of 0.5 turns per inch with a mean radius of6.4 inches and centered radially and vertically inside an outer coppershield 610. Coil 608 is operably coupled to a power source 612 andoperated at about 13 MHz radio frequency. A 17 inch long, 9.25 inchdiameter quartz tube 606 is centered inside of the copper coil 608. Theshield 610 is 16 inches inside diameter, approximately 0.08 inches thickand 18 inches long. This shield 610 also can be connected to a ground(V_(G)) connection on the aluminum process chamber body (except whenmaking the current measurements described below).

[0098] The process chamber 604 can be for a conventional resiststripper. This resist stripper included a wafer support 616 (orpedestal) and other elements. Process chamber 604 is operably coupled atan outer location 620 to ground via shield 610. Wafer support 616 has awafer 618 disposed thereon.

[0099] The wafer 618 is a 6-inch (250 mm)<100> type wafer withapproximately 1.25 microns of spin-coated positive photoresist. Thiswafer can be ashed on the grounded 10 inch diameter wafer support 616.This support can be resistivity heated and the temperature of thesubstrate support can be sensed with a thermocouple.

[0100] After the helical resonator plasma is ignited, visible plasmafilled the quartz plasma tube under all of the conditions used forprocessing. In addition, a strong plasma glow can always be visibleabove the wafer in the downstream processing chamber which wasindicative of secondary plasma discharge to the substrate support. Thissecondary plasma discharge cab also be accompanied by current flow fromthe resonator shield to the chamber of approximately 5-10 Amperes rms(and sometimes even more) which could be measured by elevating theshield on insulating blocks and monitoring the current flow through a 2inch long 1.5 inch wide strip of copper braid which is passed through aPearson Current probe used to monitor the current.

[0101]FIG. 7 is a simplified diagram 700 of the rf voltage distributionalong the coil for the quarter-wave helical resonator of FIG. 6. Thisdiagram includes the quartz tube 606 and a plasma discharge (or source)701 therein. As shown, the plasma discharge includes a glow region that701 occupies a large range (R) of the quartz tube 606. The plasmadischarge has an average voltage (V_(save)) between the ground potential(V_(G)) and the high voltage potential (V_(H)). As can be seen, theplasma discharge 701 has current flow through capacitively couplingelements to V_(H) and V_(G) and elements of elevated potential on thecoil due to its average voltage potential V_(ave). In fact, aspreviously noted, the current flow from the resonator shield to thechamber is at least 5-10 Amperes rms. In high power applications,intense sparking is observed in the chamber from the capacitivelycoupled plasma source.

[0102] II. New Photoresist Stripper

[0103] A resist stripper apparatus in a cluster tool arrangement using ahelical resonator according to the present inventions is shown in FIG. 8with a side view diagram of one of the two chambers, 901, shown in FIG.9. One of ordinary skill in the art, however, will recognize that otherimplementations, modifications, and variations may be used. Accordingly,the experiments performed herein are not intended to limit the scope ofthe claims below.

[0104] The photoresist stripper apparatus is configured with multipleprocess chambers in a cluster tool arrangement, as illustrated bysimplified top-view diagram FIG. 8 and simplified side-view diagram ofone chamber 901 in FIG. 9. Two process chambers, e.g., chamber 1 901 andchamber 2 903, are used. Chamber 1 901 is used for stripping to upperlayer of implant hardened resist (crust or skin). Chamber 2 903 is usedfor stripping the remaining underlayer of photoresist. Alternatively,both of these chambers can be used for stripping implant hardened resistcrust and stripping remaining photoresist in parallel using sequentialprocess operations. Of course, the particular use and recipe dependsupon the application. These chambers can also be made of aluminum withinserts, which are resistant to chemical attack.

[0105] The apparatus uses a microcontroller based controller to overseeprocess operations. This microprocessor based controller can be accessedthrough a control panel 921. A suitable controller can be made using a486 or Pentium processor in a conventional PCI bus-based personalcomputer. Operator access to the control recipes and process parameterscan be made using a conventional LCD touch panel display.

[0106] An automatic wafer handling system 910 is also provided. Theautomatic wafer handling system uses standard cassettes 912 fortransferring photoresist-coated wafers to and from the process chambers901, 903. The automatic wafer handling system includes a robot 917,cassette chamber 1 905, cassette chamber 2 907, cassette stage 1 909,cassette stage 2 911, and other elements. The wafer handling system 910uses a conventional interlock system for providing the cassettes 912from the cleanroom into the process chambers 901, 903. A main shuttlechamber 913 houses the robot 917 in the cluster tool arrangement. Thecontroller oversees the automatic wafer handling system operations.

[0107] Cooling plates 915 and 910 are optionally included in the mainchamber 913 housing the robot 917. The cooling plates 915 and 910 are ofconventional design, and are capable of cooling the wafer after beingstripped, which often occurs at elevated temperatures. Alternatively,the cooling plates can be used to thermally adjust the wafer temperatureeither before, after, or even between selected process operations.

[0108] The process chambers 901, 903 are disposed downstream fromrespective plasma sources 923, 925. Each helical resonator includes acoil 927 disposed around a quartz tube 929. A suitable coil consists of11.5 turns of 0.4 inch copper tubing wound with a pitch of 0.9 turns perinch with a mean radius of 9.4 inches and centered radially andvertically inside an outer copper shield 931. The coil is operablycoupled to a power source by coaxial cable 941 which is connected to asuitable matching tap point 951 on the helical coil. A 17 inch long,9.25 inch diameter quartz tube is centered inside of the copper coil.The shield is 16 inches inside diameter, approximately 0.1 inches thickand 18 inches long. The shield is operably coupled to upper and lowerportions of the coil 971.

[0109] Although the helical resonator delivers rf power to the dischargewith very high efficiency, the plasma source and applicator structuresare often strongly heated by the energy released from within the plasmadischarge chamber. Hence it is desirable to control the temperature ofthe plasma source and rf applicator structure. This is conveniently doneby means of a liquid heat transfer agent (e.g. deionized water or asuitable heat exchange fluid) which is maintained at a constanttemperature and circulated through the tubular helical coil by way offluid connections 987 and 988. Additional means for cooling the shield931 (not shown in FIG. 9) are provided for use in certain high powerapplications. It will be obvious to those skilled in the art that heattransfer utilizing a gaseous coolant (e.g. air or nitrogen) or externalconductive or convective heat transfer means can also be used in manyapplications.

[0110] Processes in this equipment may be used for stripping photoresistfrom wafers, e.g., See FIG. 9 reference numeral 933, or selected CDEoperations such as the selective removal of silicon nitride films whichhave been deposited over silicon oxide. Particular processes may involvea multi-step stripping operation to remove implanted photoresist fromsemiconductor wafers. For example, Photoresist 1.5 microns in thicknesson device wafers may be implanted. This implant operation causes theformation of an implant hardened stratum over the top of an underlyinglayer of normal photoresist.

[0111] A clean implant resist stripping process can be conveniently beperformed by stripping the top implant hardened resist layer byion-assisted ashing using an “un-balanced” coupling relationship in ahalf-wave helical resonator. A suitable half-wave helical resonator isconfigured in one of the process chambers. The half wave helicalresonator plasma chamber can be conveniently operated at a frequency ofabout 13.56 MHz corresponding to a full-wave multiple. In this chamber,the pedestal can conveniently be maintained at a low wafer temperaturein the range of 50C-80C to reduce the possibility of “popping.” Poppingoccurs when the pressure of low molecular weight monomer, oligimer orsolvent in the underlying photoresist bursts the relatively impermeableimplant hardened surface layer of the resist.

[0112] After the uppermost hardened layer of the resist is removed, thewafer is transferred into a chamber operating in a suitable balancedconfiguration such as a full-wave multiple. Plasma confinement affordedby use of the present invention avoids damaging current flow and ionbombardment to the substrate when it as exposed as the resist is“cleared” just before and after “endpoint.” The full wave helicalresonator plasma chamber can be conveniently operated at a frequency ofabout 27.12 MHz corresponding to a full-wave multiple. The pedestal ofthis chamber is generally maintained at a selected temperature in therange of 150 to 220C. It is advantageous to operate at as high atemperature as is permissible because the ashing chemical reaction rateincreases with temperature and therefore the machine productivity(throughput) will be greater. However the maximum usable temperature isoften limited by the vulnerability of device layers to harmful thermaleffects. For example, some silicon antireflection coatings require thattemperature be limited to below about 170-180C. Another limitation ontemperature is related to uniformity. Temperature uniformity in someheater configurations deteriorates with increasing temperature owing toa shift from dominantly conductive and convective heat transfer to anenergy balance in which radiative heat transfer processes have a greaterrole. In general, there are proportionately greater amounts of heatingand cooling by radiation at higher temperatures, since radiative energytransfer depends on the temperatures of surfaces which “view” each otherraised to the fourth power, whereas conductive and convective heattransfer often depend linearally on localized temperature differences.It is desirable that etching and ashing processes be highly uniform inorder that the overetch period during which all or portions of devicelayers are exposed to reactive plasma species can be minimized. Plasmainduced damage, if it occurs, is known to take place after some or allparts of device layers are exposed. (A discussion of damage andtemperature effects in resist stripping is given in “Dry Plasma ResistStripping” by D. L. Flamm in Solid State Technology, pps. 37-39, August1992 (Part I),pps. 43-48, September 1992 (Part II) and pps. 43-48,October 1992 (Part III)). A balanced structure which provides forsubstantially equal capacitive coupling to applicator elements with rfvoltages inverse to each other, in particular a balanced full wavestructure such as that described in this example provides for balancedphase and inverse-phase coupled currents, thereby reducing the amount ofcapacitively coupled plasma, which can be detrimental to the underlyingsubstrate. In this step, overashing is performed to substantially removeall photoresist material from the wafer. No damage occurs to theunderlying substrate during this overashing step.

[0113] Once the photoresist has been stripped, the wafer is cooled. Inparticular, the wafer is removed from the full-wave multiple processchamber, and placed on the cooling station. This cooling station reducesthe temperature of the wafer (which was heated). This wafer is thenreloaded back into its wafer cassette. Once all wafers have beenprocessed in the cassette, the cassette comprising the stripped wafersis removed from the cluster tool apparatus. Characteristics of thishalf-wave helical resonator were described in detail above.

[0114] Useful processing conditions for ashing 6-inch wafers with normal(not ion-implanted) photoresist are pressures in the range of 0.1 to 10Torr using a gas flow in the range of 0.1 to 10 standard liters per min.and input power to the plasma of approximately 1.5 to 2.5kW (For thispurpose power is defined to be the net power transferred to the helicalresonator structure, e.g. forward-reflected power in the transmissionfeed line, since the helical resonator is extremely efficient e.g. morethan 90% of transferred power is absorbed by the plasma). Under theseconditions an ashing rate above 3kÅ/min are readily achieved when ashinga lower temperature (e.g. c.a. 60C) and rates of 1 μ/min and higher canbe achieved when the temperature is elevated (in the range of 170-210C).When feed the feed gas flow profile is sufficiently uniform (A wideresidence time distribution of gas flow in the plasma source isundesirable. In the example the residence time is made more homogeneousby the imposition of a baffle plate 975 below the feed gas inlet 976.Ashing uniformity in a chamber geometry exemplified by FIG. 9 is mainlydetermined by temperature uniformity across the wafer. When the resistasher is equipped with a suitably designed wafer heating means such as amultizone resistive heater 981 with multiple electrical connections983-986 as shown in FIG. 9, an average etching uniformity better than 5%is readily achieved.

[0115] A visual inspection of wafers stripped in this type of apparatuscan show extremely good results. That is, the wafers are stripped at asufficient rate for production operation and no substantial damageoccurs to the wafers. This provides for effective wafer turn-around-timeand substantially no damage caused by the plasma. In addition, currentmeasured from the shield to the chamber by elevating the shield oninsulating blocks is substantially less than current(s) measured in aconventional (unbalanced) helical resonator stripping apparatus.

[0116] While the invention has been described with reference to specificembodiments, various alternatives, modifications, and equivalents may beused. In fact, the invention also can be applied to almost any type ofplasma discharge apparatus. This discharge apparatus can include anapparatus for plasma immersion ion implantation or growing diamonds,TCPs, and others. This discharge apparatus can be used for themanufacture of flat panel displays, disks, integrated circuits,diamonds, semiconductor materials, bearings, raw materials, and thelike. Therefore, the above description should not be taken as limitingthe scope of the invention which is defined by the appended claims.

What is claimed is:
 1. A device made using a process for fabricating aproduct, said process comprising the steps of subjecting a substrate toentities, at least one of said entities emanating from a speciesgenerated by a gaseous discharge excited by a high frequency field inwhich the vector sum of phase portions and inverse-phase portions ofcapacitive current coupled from the inductive coupling structure areselectively maintained.
 2. The device of claim 1 wherein said productcomprises a semiconductor device.
 3. The device of claim 1 wherein saidgaseous discharge is provided by a helical resonator.
 4. The device ofclaim 1 wherein said gaseous discharge is provided by a helicalresonator having an electrical length which is substantially a wholenumber multiple of one wavelength.
 5. The device of claim 1 wherein saidgaseous discharge is provided by a helical resonator structure, saidhelical resonator structure having an electrical length which issubstantially free from any whole number multiple of one quarterwavelength.
 6. The device of claim 1 wherein said one said entities isprovided in chemical vapor deposition.
 7. The device of claim 1 whereinsaid one of said entities is provided in plasma etching.
 8. The deviceof claim 1 wherein said inductive coupling structure is selectivelybalanced using a wave adjustment circuit.
 9. Apparatus for fabricating aproduct, said apparatus comprising: an enclosure comprising an outersurface and an inner surface, said enclosure housing a gaseousdischarge; a plasma applicator disposed adjacent to said outer surface;a high frequency power source operably coupled to said plasmaapplicator, said high frequency power source exciting said gaseousdischarge to provide at least one entity from a high frequency field inwhich the vector sum of phase and inverse-phase capacitive currentscoupled from the inductive coupling structure are selectivelymaintained; and a wave adjustment circuit, said wave adjustment circuitoperably coupled to said plasma applicator to selectively maintain saidinductive coupling structure.
 10. Apparatus of claim 9 wherein saidenclosure is a chamber.
 11. Apparatus of claim 9 wherein said enclosureis a tube.
 12. Apparatus of claim 11 wherein said tube is made of one ormore materials selected from quartz, glass, diamond, polymer, sapphire,ceramic and alumina.
 13. Apparatus of claim 9 wherein said apparatus isprovided for chemical vapor deposition.
 14. Apparatus of claim 9 whereinsaid apparatus is provided for plasma etching.
 15. Apparatus forfabricating a product, said apparatus comprising: a high frequency powersource operably coupled to an inductive plasma applicator, said highfrequency power source exciting a gaseous discharge to provide at leastone entity from a high frequency field in which a vector sum of couplingto phase and inverse phase voltage elements from the inductive couplingstructure are selectively maintained; and a wave adjustment circuit,said wave adjustment circuit operably coupled to a plasma applicator toselectively adjust said inductive coupling structure.